VALENCIA — A U.N. climate change conference argued over words and phrases Wednesday in drafting a scientific report that will guide governments for years to come on their global warming policies.

One dispute involving the U.S. delegation centered on whether human activity could lead to 'abrupt or irreversible' effects on the Earth's climate, said participants in the meeting.Another focused on India's concerns over 'adaptation' to global warming, a notion that implies greater financial aid to developing countries, participants said on condition of anonymity since the talks were confidential.They were just two of many unresolved issues raised during the third day of talks among delegations from more than 140 countries, advised by the scientists who drew up the text.Negotiators described the talks as moving 'very slowly.' Disputes were moved into small working groups to expedite their resolution.The Nobel Prize-winning Intergovernmental Panel on Climate Change is preparing a report about 20 pages long summarizing the scientific consensus on the causes and effects of climate change and possible measures to slow the Earth's temperature increase. The summary draws on thousands of pages of scientific evidence and computer models.The report was due to be released Saturday by U.N. Secretary-General Ban Ki-moon. It will then become a reference for nations gathering next month in Bali, Indonesia, to discuss the next stage in global efforts to control emissions from greenhouse gases blamed for the warming trend.The document being debated in Valencia is important because it is approved by consensus, meaning that all participating governments subscribe to its findings.But nations were fighting hard to defend their own interests.The participants said the United States was objecting to a sentence in the draft that said: 'Human activities could lead to abrupt or irreversible climate changes and impacts.'U.S. delegates argued that terms like 'irreversible' were unscientific and inappropriate in the summary, the participants said. Others countered that nothing was reversible about the extinction of species or the melting of polar ice sheets, as the scientists predict in some scenarios, the informants said.The report, the fourth to be issued this year, is a composite of the three earlier reports. The World Wide Fund for Nature blamed some countries earlier this week for insisting on changes in the previous summaries to mute the potentially disastrous affects of climate change and to dilute calls for urgent action.In another dispute, the informants said India sought to break the link in the draft between adaptation and mitigation, and toughen the language to reinforce the need to adapt to changing climatic conditions.An early draft obtained by The Associated Press would put the onus on countries to both adapt to, and act against, climate change. It says: 'Neither adaptation nor mitigation alone can avoid significant climate change impacts, however, they can complement each other and together can significantly reduce the risks of climate change.'India has argued that carbon emissions from industrialized countries were to blame for global warming, and they should help poorer countries finance efforts to adapt to the consequences. India also says its potential for economic development should be unfettered by obligations to control emissions.